#define _CRT_SECURE_NO_WARNINGS 1
#include<iostream>
using namespace std;
double n;
int main()
{
    scanf("%lf", &n);
    double l = 0, r = n;
    if (n > 0)
        l = 0, r = n;
    else
        l = 0, r = -n;
    while (r - l > 10e-8)
    {
        if (n >= 1 || n <= -1)
        {
            double mid = (l + r) / 2.0;
            if (mid * mid * mid > abs(n)) r = mid;
            else l = mid;
        }
        else
        {
            double mid = (l + r) * 2;
            if (mid * mid * mid > n) l = mid;
            else r = mid;
        }
    }
    if (n > 0)
        printf("%.6lf", l);
    else
        printf("%.6lf", -l);
    return 0;
}